In the course of the Fukushima nuclear accident, radionuclides were released in various forms, including so-called radiocesium-bearing microparticles (CsMP). So far, four types of CsMP were ...described: Type A is smaller in size (< 10 μm), Types B, C, and D are larger (> 100 μm). In this work, we present a novel type of CsMP (proclaimed Type E). Three particles of Type E were extracted from a contaminated blade of grass that was sampled 1.5 km from the Fukushima Daiichi nuclear power plant in late 2011. They were located using autoradiography, isolated using an optical microscope and micromanipulator, and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, and low-level gamma-ray spectrometry. Type E CsMPs are 10–20 μm in size and exhibit an unusually low and barely detectable
137
Cs activity of only ≤ 10 mBq per particle. Their brittle and fragile character may indicate a high surface tension.
The long-lived fission product
151
Sm (T
1/2
≈ 90 y) present in archived dissolved Trinity nuclear test debris samples was analyzed using liquid scintillation counting and the results were compared ...to the expected values based upon historical analysis results. The measured
151
Sm activities were found to agree with the expected values within experimental error. This demonstration validates the use of this technique in situations where the sample is too old for traditional shorter half-life radioactive fission product signatures such as
99
Mo (T
1/2
= 2.75 d),
97
Zr (T
1/2
= 16.7 h),
147
Nd (T
1/2
= 10.98 d), and
153
Sm (T
1/2
= 46.3 h), or too dilute for determining fissions through stable isotope ratio measurements.
The accurate interpretation of uranium metal
230
Th/
234
U and
231
Pa/
235
U radiochronometry model ages requires an understanding of how uranium parent nuclides and decay progeny (
230
Th and
231
...Pa) behave during uranium metal casting. In order to directly measure the spatial distribution of
230
Th and
231
Pa in uranium metal before and after vacuum induction melting (VIM), Los Alamos National Laboratory identified uranium metal feedstock, characterized the metal feedstock, conducted a controlled casting experiment of an approximately 120 kg uranium metal rod, and characterized the cast metal. This study presents radiochronometry results and quantified
230
Th and
231
Pa VIM separation factors from bulk uranium.
Rapid and efficient isolation of individual rare earth element (REE) radioisotopes from complex mixtures is necessary to support the fields of nuclear forensics, medical isotope production and ...nuclear physics measurements. The separations must be robust and generate sufficiently high purity samples for subsequent radiological analysis. Current methodologies utilize a laborious two step Ce(IV)-iodate precipitation followed by Ce(IV)-nitrate di-(2-ethylhexyl)phosphoric acid/n-heptane extraction. This work reports an alternative method to isolate Ce fission product isotopes equilibrated with milligrams of cold carrier, from the remaining REE’s using a Ce(IV)/LN-resin (Eichrom Technologies) based separation. Optimization of Ce(IV) loading, REE(III) elution volume and subsequent Ce(III) stripping step utilized
166m
Ho tracer. Mixed fission product experiments provided a further test of this LN-resin method, with analysis of purified
141/144
Ce,
147
Nd and
91
Y. While decontamination factors were lower for the LN-resin method, (vs. the combined precipitation/extraction) the simplicity of the technique and the satisfactory fission product analysis results point to the efficacy of this method.
A radioanalytical method was developed for the determination of trace plutonium and neptunium in samples composed primarily of uranium. The procedure uses a neodymium oxalate co-precipitation and a ...two-column separation using ion exchange resin to achieve high uranium decontamination, high plutonium and neptunium separation factors and low impurity levels. The separation of the three actinides from each other relies on their oxidation–reduction chemistry. Various measurement techniques can be applied to determine plutonium and neptunium in the purified fractions: i.e., alpha spectrometry, and thermal ionization mass spectrometry. The method development, validation, and applications are discussed.
The plutonium rapid response in vitro bioassay method described here was designed to determine
238
Pu,
239
Pu, and
240
Pu concentration in urine samples from workers with potential internal ...contamination. Results provide quick and actionable information about the level of contamination necessary to assist making further medical decisions, including chelation therapy. The radiochemical procedure can be performed within approximately 48 h, including sample preparation, measurement(s) by alpha spectrometry and/or inductively coupled plasma mass spectrometry (ICP-MS), and data evaluation.
The long-lived fission product .sup.151Sm (T.sub.1/2 almost equal to 90 y) present in archived dissolved Trinity nuclear test debris samples was analyzed using liquid scintillation counting and the ...results were compared to the expected values based upon historical analysis results. The measured .sup.151Sm activities were found to agree with the expected values within experimental error. This demonstration validates the use of this technique in situations where the sample is too old for traditional shorter half-life radioactive fission product signatures such as .sup.99Mo (T.sub.1/2 = 2.75 d), .sup.97Zr (T.sub.1/2 = 16.7 h), .sup.147Nd (T.sub.1/2 = 10.98 d), and .sup.153Sm (T.sub.1/2 = 46.3 h), or too dilute for determining fissions through stable isotope ratio measurements.
•Actinium-225 (t1/2=9.92d) is an α-emitting radionuclide for use in targeted alpha therapy.•During proton irradiation of thorium metal, long-lived 227Ac (t1/2=21.8a) is co-produced.•An efficient ...Ac/Th separation procedure is required for rapid 225Ac/227Ac ratio determination.•For Ac isolation, a sequence of cation exchange and extraction chromatography was implemented.•Ac is isolated from Th and then purified from fission lanthanides via extraction chromatography.
Actinium-225 (t1/2=9.92d) is an α-emitting radionuclide with nuclear properties well-suited for use in targeted alpha therapy (TAT), a powerful treatment method for malignant tumors. Actinium-225 can also be utilized as a generator for 213Bi (t1/2 45.6min), which is another valuable candidate for TAT. Actinium-225 can be produced via proton irradiation of thorium metal; however, long-lived 227Ac (t1/2=21.8a, 99% β−, 1% α) is co-produced during this process and will impact the quality of the final product. Thus, accurate assays are needed to determine the 225Ac/227Ac ratio, which is dependent on beam energy, irradiation time and target design. Accurate actinium assays, in turn, require efficient separation of actinium isotopes from both the Th matrix and highly radioactive activation by-products, especially radiolanthanides formed from proton-induced fission. In this study, we introduce a novel, selective chromatographic technique for the recovery and purification of actinium isotopes from irradiated Th matrices. A two-step sequence of cation exchange and extraction chromatography was implemented. Radiolanthanides were quantitatively removed from Ac, and no non-Ac radionuclidic impurities were detected in the final Ac fraction. An 225Ac spike added prior to separation was recovered at ≥98%, and Ac decontamination from Th was found to be ≥106. The purified actinium fraction allowed for highly accurate 227Ac determination at analytical scales, i.e., at 227Ac activities of 1–100kBq (27nCi to 2.7μCi).
In the course of the Fukushima nuclear accident, radionuclides were released in various forms, including so-called radiocesium-bearing microparticles (CsMP). So far, four types of CsMP were ...described: Type A is smaller in size (< 10 μm), Types B, C, and D are larger (> 100 μm). In this work, we present a novel type of CsMP (proclaimed Type E). Three particles of Type E were extracted from a contaminated blade of grass that was sampled 1.5 km from the Fukushima Daiichi nuclear power plant in late 2011. They were located using autoradiography, isolated using an optical microscope and micromanipulator, and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, and low-level gamma-ray spectrometry. Type E CsMPs are 10–20 μm in size and exhibit an unusually low and barely detectable 137Cs activity of only ≤ 10 mBq per particle. Their brittle and fragile character may indicate a high surface tension.
Abstract
Accelerator production of
225
Ac addresses the global supply deficiency currently inhibiting clinical trials from
establishing
225
Ac's therapeutic utility, provided that the accelerator ...product is of sufficient radionuclidic
purity for patient use. Two proton activation experiments utilizing the stacked foil technique between 40 and
200 MeV were employed to study the likely co-formation of radionuclides expected to be especially challenging to
separate from
225
Ac. Foils were assayed by nondestructive
γ
-spectroscopy and by
α
-spectroscopy of
chemically processed target material. Nuclear formation cross sections for the radionuclides
226
Ac and
227
Ac as well as lower lanthanide radioisotopes
139
Ce,
141
Ce,
143
Ce, and
140
La whose elemental ionic radii closely match that of actinium were measured and are reported. The predictions of
the latest MCNP6 event generators are compared with measured data, as they permit estimation of the formation rates of other
radionuclides whose decay emissions are not clearly discerned in the complex spectra collected from
232
Th(p,x)
fission product mixtures.
PDF
